The invention relates to a nut for fixing releasable components, such as machine elements, which are subjected during operational use to an increased risk of the fixed and reliable arrangement becoming loose, for example, as a result of vibrations. The particularly preferred field of application of the invention relates to wheel nuts or axle nuts for vehicles. Nuts of the generic type are provided with a nut body, a central threaded hole, a peripheral wall, an abutment face at a lower side of the nut and a plurality of wrench faces on the peripheral wall of the nut body for tightening or releasing the nut by means of a tool which cooperates with the wrench faces. The invention also relates to washers for use with corresponding nuts, in particular with wheel nuts or axle nuts for vehicles, having a disc body, a central hole, a peripheral wall, an abutment face on a lower side of the disc body and an abutment face on an upper side of the disc body. With regard to the main application field of the invention, that is to say, the securing of vehicle wheels or wheel bearings on the axles of vehicles, the invention also relates to a control device for wheel or axle nuts in vehicles which have at least one wheel bearing which is fixed to a vehicle axle by means of an axle nut and/or at least one vehicle wheel which is fixed to a wheel hub by means of a wheel nut and which are provided with an on-board electronic unit, via which information from sensor elements can be displayed for the vehicle driver, wherein the wheel nut and/or the axle nut are provided with a nut body, a central threaded hole, a peripheral wall, an abutment face at a lower side of the nut and a plurality of wrench faces on the peripheral wall of the nut body for tightening or releasing the nut by means of a tool which cooperates with the wrench faces, and further also vehicles provided with such a control device.
In road traffic, accidents may occur as a result of a large number of different causes, it being possible for particularly a technical failure on the vehicle or vehicle components also to constitute such a cause in addition to human error. In commercial vehicles but also in private cars, the fixed arrangement of the wheel nuts with which a vehicle wheel is fixed to a wheel hub is checked only rarely. Not only after a wheel has been changed but also as a result of the daily operational use of the vehicle on the road, individual wheel nuts may become loose, which may already lead to extreme situations when travelling round bends, such as a loss of control over the vehicle or even damage to the tyres or a vehicle wheel becoming loose. The axle nuts with which a wheel bearing which generally comprises the wheel hub and the brake disc is secured to the axle of a vehicle can also become loose or may be mounted incorrectly after, for example, a brake disc has been changed.
For commercial vehicles such as buses, lorries, refuse vehicles, vehicles for transporting hazardous goods and utility vehicles, there are often used wheel nut indicators which are available in extremely varied wrench widths and which are constructed depending on the configuration either as a ring with a marking arrow or as a cap with a marking arrow, and are fixed after a wheel change to the wheel nut which was preferably tightened with a predetermined torque. The greatest level of safety for the vehicle driver is then ensured if each wheel nut on each vehicle wheel is provided with a corresponding indicator, wherein two adjacent wheel nuts generally form a pair, in which the indicators are mounted in such a manner that the arrow tips are directed towards each other. It is then possible for the vehicle driver to check for a wheel nut becoming loose by means of a visual inspection of all the vehicle wheels. If, however, there are used wheel caps which cover the wheel nuts, it is not possible to use corresponding indicators in an advantageous manner. There is further the risk that the indicators become stolen or become loose. By suitable plastics materials being selected, an excessively powerful generation of heat in brakes can also be signalled with the indicators, that is to say, if the melting point is so low that the indicators become deformed or melt.
DE 20 2004 051 865 B4 discloses an electronic wheel securing system for wheel nuts. Each individual wheel bolt is provided with an insulated contact pin whose free pin end protrudes beyond the upper side of the wheel bolt. The outer thread portions of the individual wheel bolts are partially insulated and all the wheel bolts are connected to each other via contact rails in such a manner that a wheel nut which is screwed onto the wheel bolt engages in the region of the fixing location thereof through an insulation of the contact pin and thereby closes a circuit between the wheel bolt and contact rail. If the wheel nuts become loose by a necessary minimum dimension of at least one thread turn, the contact is interrupted, whereby there is produced an electrical impulse which is indicated acoustically and/or optically as a warning signal for the vehicle driver. Such a system is very passive and reacts only when the screw has become loose to such an extent that under some circumstances dangerous situations may already occur. It is further disadvantageous for the contact rail to have to be acted on permanently with electric current.